The normal wall-mounted switch used, qualitatively, to control the application of electrical power to an electric light or other load in a residence is, of course, quite effective over relatively extended periods under normal environmental conditions. However, this type of switch involves the mechanical motion of metal contacts into or out of physical contact and limitations on its useful life even under normal environmental conditions are found. More particularly, even though relatively small amounts of power must be delivered, the spacing of the contacts must be maintained at a minimum amount to preclude inadvertent arcing, for example, when high local humidity reduces the effective resistance between the separated contacts. Accordingly, considerable motion is required to provide a useful switch and this, in turn, limits the useful life typically to approximately 100,000 opening and closing operations. If the humidity is quite high or other environmental conditions, such as operation in a submarine or the like where more moisture exists, are encountered the useful life is much more limited because of chemical action and the arcing experienced as the switch contacts approach their closure position.
To overcome these defects, attempts have been made to avoid the necessity for direct mechanical contact of two conductors, a known example being the capacitively-operated switches found quite commonly on elevators and the like, but these too are adversely affected by a change in humidity or other environmental conditions which affect the dielectric of the capacitor. While certain problems of the simple mechanical switch are eliminated, these additional problems have created, in certain instances, serious malfunctions.
While, as indicated hereinabove, malfunctions in existing switches or other devices which provide a qualitative signal control are significant, yet more critical significance in quantitative control functions are experienced with existing control mechanisms. For example, in the case of some electronic organs using certain types of oscillator circuits, a change in humidity "detunes" the oscillators and expensive measures have been taken to avoid this problem of inadvertent frequency variation.